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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the admittance-frequency and capacitance–voltage of dense SnO2⋅CoO-based varistor ceramics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 6007-6014 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes the admittance-frequency feature of a class of SnO2⋅CoO-based polycrystalline ceramics with high nonlinear current–voltage characteristics (nonlinear coefficients above 50). Broad relaxation peaks caused by the presence of deep trap states were characterized based on the admittance response of different systems doped with La2O3, Pr2O3, and CeO2. The calculation of the energy of this deep trap level revealed not only that all the compositions share the same value but also that this value could be attributed to an oxygen vacancy or to CoSn[partial lengthening] like defects. The values of barrier height and density of states obtained from a capacitance–voltage analysis are in good agreement with the nonlinear coefficients. The highest nonlinear coefficients are found in compositions with greater barrier height values and higher density of deep trap states at the grain boundary interface. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1455685
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  • 2
    Electronic Resource
    Electronic Resource
    Role of oxygen at the grain boundary of metal oxide varistors: A potential barrier formation mechanism (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 48-50 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model is proposed here to explain how the chemical features of metal oxide varistors can alter their nonohmic physical behavior, based on nonohmic similarities in the electrical properties of ZnO- and SnO2-based varistors. The proposed model explains the electrical properties of ZnO- and SnO2-based varistors before and after thermal treatments in oxygen- and nitrogen-rich atmospheres, which cause similar changes in the nonohmic feature of these polycrystalline ceramics with greatly differing chemical compositions and microstructures. The model is based on the key role that oxygen plays in varistor grain boundaries, independently of the type of ceramic system (ZnO-, SnO2- or even SrTiO3-based varistors) involved. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378051
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  • 3
    Electronic Resource
    Electronic Resource
    The RNase PD2 gene of almond (Prunus dulcis) represents an evolutionarily distinct class of S-like RNase genes (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 925-933 
    Details
    ISSN: 1617-4623
    Keywords: Key words S-like RNase ; Phosphate starvation ; Senescence ; RFLP ; Almond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA for an S-like RNase (RNase PD2) has been isolated from a pistil cDNA library of Prunus dulcis cv. Ferragnés. The cDNA encodes an acidic protein of 226 amino acid residues with a molecular weight of 25 kDa. A potential N-glycosylation site is present at the N-terminus in RNase PD2. A signal peptide of 23 amino acid residues and a transmembrane domain are predicted. The two active-site histidines present in enzymes of the T2/S RNase superfamily were detected in RNase PD2. Its amino acid sequence shows 71.2% similarity to RNS1 of Arabidopsis and RNase T2 of chickpea, respectively. Northern blotting and RT-PCR analyses indicate that PD2 is expressed predominantly in petals, pistils of open flowers and leaves of the almond tree. Analyses of shoots cultured in vitro suggested that the expression of RNase PD2 is associated with phosphate starvation. Southern analysis detected two sequences related to RNase PD2 in the P. dulcis genome. RFLP analysis showed that S-like RNase genes are polymorphic in different almond cultivars. The PD2 gene sequence was amplified by PCR and two introns were shown to interrupt the coding region. Based on sequence analysis, we have defined three classes of S-like RNase genes, with the PD2 RNase gene representing a distinct class. The significance of the structural divergence of S-like RNase genes is further discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380000258
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  • 4
    Electronic Resource
    Electronic Resource
    PD1, an S-like RNase gene from a self-incompatible cultivar of almond (2000)
    Springer
    Plant cell reports 19 (2000), S. 1108-1114 
    Details
    ISSN: 1432-203X
    Keywords: Key words Almond ; cDNA cloning ; Prunus dulcis Sequence comparison ; S-like RNase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Many flowering plants contain stylar S-RNases that are involved in self-incompatibility and S-like RNases of which the biological function is uncertain. This paper reports the deduced amino acid sequence of an S-like RNase gene (PD1) from the self-incompatible plant Prunus dulcis (almond). The amino acid sequence of PD1, which was derived from cDNA and genomic DNA clones, showed 34–86% identity to acidic plant S-like RNases reported so far, with the highest degree of similarity being to an S-like RNase from Japanese pear (Pyrus pyrifolia). Based on RNA hybridisation experiments it appears that, like for many other S-like RNases, the expression of PD1 is not pistil-specific. Analysis of the genomic structure revealed the presence of three introns, of which one is similar in location to that of the related S-RNase gene from Solanaceae and Rosaceae. At least four bands hybridising to PD1 were found upon Southern hybridisation, suggesting the presence of a multigene family of S-like RNase genes in almond. The putative biological function of PD1 is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990000235
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